1. Field of the Invention
The present invention relates to a manufacturing apparatus of a master disc by irradiating an electron beam on a substrate.
2. Description of the Related Art
A variety of large-capacity recording media are under development for recording image/audio data and digital data thereon. An optical disc such as a DVD (Digital Versatile Disc) is one example of the recording media. Research and development are now under progress for increasing the recording capacity to, for example, 30 GB (Giga-Bytes) for the optical disc having a diameter of 12 cm. Also, a hard disk platter for magnetic recording having large capacity is also under development.
Recording resolution, however, is limited by the spot diameter of a laser beam for recording in the manufacturing process of a master (i.e., a master disc or a stamper) of a recording medium using a conventional laser beam in a visible or ultraviolet wavelength range. Investigations have been made for manufacturing the master (i.e., cutting of the master) with a master manufacturing apparatus using an electron beam for increasing the recording density of the disc, since the electron beam has a smaller spot diameter than a visible or ultraviolet laser beam.
Such a high-density disc, for example, the DVD has a very fine track pitch of 1 xcexcm or less. Further improving the density requires that the track pitch be made smaller. This demands not only high precision control on an electron beam but also a high precision operation of a drive unit which rotates and moves a substrate for the master disc. Particularly, it is necessary to perform high precision control on the rotational fluctuation or the like that is produced in such a drive unit. However, a practical master manufacturing apparatus capable of preparing high-precision masters has not appeared yet.
The present invention has been made in view of the problems mentioned above, and the object of the present invention is to provide a high precision master manufacturing apparatus which is capable of manufacturing a high-density disc.
To achieve the object, according to one aspect of the present invention, there is provided an apparatus for manufacturing a master by irradiation of an electron beam on a substrate mounted on a turntable, which comprises an electron-beam emitting section for emitting the electron beam; a focus control section for converging the electron beam on a principal surface of the substrate; a rotation drive section for rotating the turntable; a movement drive section for relatively moving the electron-beam emitting section and the turntable in a predetermined direction in a plane parallel to the principal surface; a first correction-signal generating section for detecting a first asynchronous component of rotational fluctuation of the turntable in the predetermined direction to generate a first correction signal; a second correction-signal generating section for detecting a second asynchronous component of rotational fluctuation of the turntable in a direction perpendicular to the predetermined direction to generate a second correction signal; and a deflection control section for performing deflection control on the electron beam on the basis of the first correction signal and the second correction signal.
According to another aspect of the present invention, there is provided an apparatus for manufacturing a master by irradiation of an electron beam on a substrate, which comprises an electron-beam emitting section for emitting the electron beam; a deflection drive section for performing deflection control on the electron beam; a rotation drive section for rotating the substrate; a movement drive section for relatively moving the electron-beam emitting section and the substrate in a predetermined direction in a plane parallel to a principal surface of the substrate; a distance measuring section for measuring an displacement amount of the substrate in the predetermined direction when the substrate is rotated; an asynchronous-component generating section for calculating a weighted mean value of a current displacement amount measured by the distance measuring section and an accumulated displacement amount and for subtracting the calculated weighted mean value from the measured current displacement amount to generate an asynchronous component, the accumulated displacement amount being a previous weighted mean value for one rotation of the substrate; and a control section for controlling the deflection drive section based on a magnitude of the asynchronous component to thereby adjust an irradiation position of the electron beam.